The present invention relates to gas turbine engines. In particular, the invention relates to the mounting of air turbine starters on accessory gearboxes.
Gas turbine engines require a significant torque be applied to rotate a compressor in the gas turbine, and thereby to provide sufficient compression to start the engine. Electric motors powerful enough to provide such torque can be used, but are relatively heavy. Where gas turbine engines are used for transportation purposes, for example, aircraft propulsion and power, such an extra weight penalty is undesirable. An air turbine starter (ATS) is generally employed as a substitute in such applications. The ATS is powered by compressed air from an external source. The compressed air passes over blades of an air turbine in the ATS and exits the ATS through an air exit port. As the air turbine rotates, it rotates a series of shafts connected to the compressor in the gas turbine engine, providing sufficient torque to start the engine.
For many gas turbine engines, the ATS is a stand alone line replaceable unit (LRU) that is mounted to the accessory gearbox. The ATS includes an overrunning clutch assembly that selectively couples the ATS's transmission to the output shaft. The overrunning clutch is supported by dedicated clutch bearings that are in turn supported by a separate transmission housing of the ATS. These features add size, weight, and cost to the ATS.